There appears to be a wealth of information regarding the historical context of Shakespeare's play "King Lear". You may be interested in having a look at information that I believe is relevant to your question using the following link:
In terms of themes, some of the prominent themes within this play include:
- Nihilism - Nihilism is the idea and belief that life is meaningless and therefore values are baseless. It is a motif presented in King Lear that rejects the idea of universal moralities in human nature and denies the absence of moral truths. In King Lear, nihilism presents itself in the first act where Cordelia will not praise her father.
- Justice - Essentially, there are three types of justice in "King Lear". They are human, social and divine.
- Reconciliation - Darkness and unhappiness pervade King Lear, and the devastating Act 5 represents one of the most tragic endings in all of literature. Nevertheless, the play presents the central relationship, that of Lear and Cordelia, as a dramatic embodiment of true, self-sacrificing love.
I hope this helps!